It is known that reinforcing fillers such as carbon black and silica greatly improve the strength and fatigue properties of elastomeric compounds. It is also known that chemical interaction occurs between the elastomer and the filler. For example, good interaction between carbon black and highly unsaturated elastomers such as polybutadiene (BR) and styrene butadiene copolymers (SBR) occurs because of the large number of carbon-carbon double bonds present in these copolymers. Butyl elastomers may have only one tenth, or fewer, of the carbon-carbon double bonds found in BR or SBR, and compounds made from butyl elastomers are known to interact poorly with carbon black. For example, a compound prepared by mixing carbon black with a combination of BR and butyl elastomers results in domains of BR, which contain most of the carbon black, are butyl domains which contain very little carbon black. It is also known that butyl compounds have poor abrasion resistance.
Canadian Patent Application 2,293,149 shows that it is possible to produce filled butyl elastomer compositions with improved properties by combining halobutyl elastomers with silica and specific silanes. These silanes act as dispersing and bonding agents between the halogenated butyl elastomer and the filler. However, one disadvantage of the use of silanes is the evolution of alcohol during the process of manufacture and potentially during the use of the manufactured article produced by this process. Additionally, silanes significantly increase the cost of the resulting manufactured article.
Co-pending Canadian Patent Application 2,339,080 discloses filled least one basic nitrogen-containing group and at least one hydroxyl group enhance the interaction of halobutyl elastomers with carbon-black and mineral fillers, resulting in improved compound properties such as tensile strength and abrasion (DIN).
Co-pending Canadian Patent Application 2,368,363 discloses filled halobutyl elastomer compositions comprising halobutyl elastomers, at least one mineral filler and at least one silazane compound. However, due to the low flashpoint of certain silazane compounds, such as HMDZ, the search for additional processing aids for use in silica filled butyl compounds is ongoing.